In prior art systems for transmitting binary data optically, the optical signal that is transmitted generally takes the form of an optical carrier wave that is amplitude modulated at a timing rate set by a clock. The transmitted signal then propagates through optical fibers, communication nodes and other optical telecommunication devices. As it propagates, in particular over long distances, the data signal is subjected to optical losses and is modified. It is therefore necessary to regenerate the signal to compensate cumulative unwanted noise, distortion of the signal, and time shifts.
All-optical reshaping, resynchronization, and re-amplification (3R) devices are currently at the design and development stage in research laboratories. The paper entitled “Novel Polarization-insensitive Synchronous Modulator for 20 Gbit/s All-optical Regeneration”, D. Rouvillain et al., OFC 2002, TuN3, pp. 83-84, Anaheim, 2002 discloses a complex 3R regenerator. The regenerator includes an erbium-doped fiber amplifier (EDFA), a resynchronization subsystem that includes an optical cavity incorporating a saturable absorber, and an optical clock recovery system that includes a device for converting a portion of the optical data signal to be regenerated into an electronic signal which, after filtering, controls a Mach-Zehnder electro-optical modulator performing electronic to optical conversion. The modulator has its input coupled to a DC biased laser diode and outputs the optical clock in the form of a stream of pulses. After passing through the EDFA, the optical data signal to be regenerated is injected into the saturable absorber with the optical clock, previously delayed by means of an optical delay line. Reshaping of the signal is achieved by propagation in an optical fiber using a combination of non-linear (Kerr) effects and chromatic dispersion.
However, 3R regeneration is not suitable for and/or beneficial at all stages of data signal transmission, for example at the start of transmission or on reception. This type of device is not optimized for operation with all-optical telecommunication equipment (photodetectors, monitoring modules, transmission error correcting means).